A bone fracture is a traumatic disruption of the continuity of a bone. If there is relative motion of the bone fragments at the fracture site, irritation of the surrounding tissues and heavy pain ensue and the time of fracture healing is usually extended. Proper rejoining of bone fragments is thus dependent upon immobilization of the fracture site. Classically, bone fragment reduction (bone fragments properly aligned and abutted along the fracture line or lines) and immobilization for limb bones has been accomplished by external limb casts. Such casts must be worn for long periods of time, are heavy and unbalancing to the body skeletal structure and muscular system, inhibit bone vascularity (promotes fast and effective bone healing), and may result in bone resorption because of the total absence of tensile and compressive functional loading throughout the fractured bone structure. Fractures in bones other than the arms and legs are more difficult to immobilize and the use of exterior casts may not be possible, particularly in the facial areas.
Over the past twenty years the use of stabilization and compression plate techniques for internal fixation of fractures has been developed and widely applied. With internal fixation, by means of bone screws and plates particularly plates made of biocompatible metals and metal alloys such as titanium, stainless steel and cobalt-chromium), immediate and absolute immobilization is achieved through interfragmentary stabilization and compression. Other materials and devices such as wires, intramedullary nails or externally fixed pins are used mainly to reduced bone fracture mobility and improve the position of the fracture segments. The aim of internal bone fracture fixation is to allow early, pain-free movement and use of the injured limb, mandible, etc., thus avoiding the consequences of long lasting immobilization, i.e., bone fracture disease, bone resorption, etc.
With internal bone fixation it is important that the application of the stabilization or compression plate or fracture reduction device result in relative immobility of the bone fragments and tight closure of the fracture interface or fracture interfaces. Without such immobility and tight closure, changing tension and compression loads tend to produce relative motion between the fracture fragments with resultant undesirable fragment shortening due to bone resorption. Through the proper use of a bio-compatible metallic fracture reduction device (a surgically applied implant), static forces applied as interfragmentary compression by the device prevent relative motion between the fracture interfacing surfaces. Thus, compressive pre-loading of the bone fragments (through the stabilization or compression device) prevents relative motion at the fracture site in spite of functional use of the limb, mandible, etc., without external immobilization or splinting. With mechanical stimuli (forces and motion) permitted via the internal bone fixation techniques, rapid and healthy healing of the fracture is promoted and bone vascularity is maintained and restored. Vascularity of bone is interrupted by the fracture trauma and by surgical intervention (application of the bone fixation device or devices) but revascularization is restored and enhanced by the rigid immobilization of the bone fragments or fracture interfaces through internal fixation techniques.
During the early application of stabilization and compression device techniques, the devices were meant to be merely fixed to the bone fragments of the fracture for alignment purposes. Later, the value of interfragmentary compression, through devices and plates applied under tension, was recognized. A number of internal fixation devices have been developed with built-in compression devices--devices for tensioning the device or plate to create interfragmentary compression. Some of such systems have required that the plate-tensioning device remain implanted with the plate. Other systems have been designed with removable plate-tensioning apparatus.
Further developments in compression plate designs and attachment screws (also formed of bio-compatible metals and metal alloys--particularly titanium) have related to screw head and screw hole geometry, i.e., conical geometry of the screw shoulder and oval screw holes in the compression plate for promoting bone fragment compression during screw application. Attempts to obtain optimal stability of fixation have most recently resulted in the use congruent fitment between screw head and screw hole including both conical counter-sunk screw holes and hemicylindrical screw holes.
Numerous problems remain in the application of the various compression plate systems that are commercially available for internal bone fixation. Some systems require great care in the installation of bone screws so that their orientation is always perpendicular to the plate. When contouring a plate to fit a curved bone surface, circularly fitting screw holes may become distorted and cause high friction against screw rotation or may completely inhibit a screw from entering the screw hole. Buckling or kinking of bone fragments at the fracture line may occur as a result of improper tensioning at the end of the compression plate during plate application.
In the last 10-15 years titanium mesh sheets and strips have gained wide-spread use in reconstructive, orthognathic and trauma surgery with excellent clinical results and implant survival rates. The malleability of such sheets and strips allows quick and easy bending for adaption to bone contours. In more recent years small bone plates in numerous configurations have come into high use in maxillofacial reconstructive surgery with such plates being deformable and contourable for fitment to virtually every fracture or osteotomy no matter how complex or how irregular the surgical site. Thus, contourable bone plates of "Y", "T", "L" and "I" shape configurations, and of more complex geometrical shapes, are available in a variety of thicknesses and with a selection of degrees of malleability.
Many of the implantable titanium mesh sheets and strips, and titanium plates, as described above, are relatively small (25-40 mm. in their major dimension) and difficult to maneuver into, and hold at, the appropriate fracture site location during affixation to bone fragments, particularly in maxillofacial areas which have experienced severe trauma. It is also of concern to the entire medical community dealing with implantable devices and products that material biocompatibility, durability and structural integrity, and sterility be assured in compliance with increasing interest in and control by the Food and Drug Administration in the United States.
It is a principal object of the present invention to provide unique implantable bone fracture reduction devices of relatively small but effective structure which can be easily manipulated and applied in surgical procedures involving the internal fixation of fractures.
It is a further object of the invention to provide perforated metallic sheets and strip and metallic bone plates, for use as implantable devices in the internal reduction and fixation of bone fractures, which may be easly and rapidly installed over complex or irregular surgical sites, and which have associated therewith a removable tag portion for handling of the devices during their installation and for thereafter providing identifying historical information respecting the type and structural integrity of such devices.
It is a still further object of the invention to provide relatively small implantable bone fracture internal fixation devices which may be easily held and manipulated by removable identifying implant tag portions which provide historical information respecting the type and manufacturing and structural integrity of such devices.
It is yet another object of the invention to provide small implantable metallic bone fracture internal fixation devices which may be easily held and manipulated by integral, removable identifying implant tag portions which are metallurgically identical to the implantable devices and which comprise a "witness sample" of the devices for archiving and subsequent retrieving to yield historical information respecting the product type, material specifications, manufacturing procedures and quality controls applicable to such devices.
Other objects and advantages of the invention will be apparent from the following summary and detailed description of the bone fracture reduction and fixation devices of the invention taken together with the accompanying drawing figures.